This invention relates to valves for controlling the flow of fluids, and particularly to block-and-bleed valves assembled together to form manifolds for controlling the flow of fluids from multiple sources to multiple delivery destinations. Certain concerns unique to the sanitary industry are discussed.
It is common in the food packaging industry to have a need to connect a number of sources of a fluid, such as different types of milk, to a number of different filler machines to fill containers, such as gallons, half-gallons, quarts and so on. To date these connections have been accomplished in the form of a manifold, including a number of lines from the source tanks crossing a number of lines leading to the filler machines, with the valves being provided to permit or prevent flow of fluid from any selected one or more of the source tanks to any chosen one or more of the filler machines. This arrangement creates a need for an extremely large number of valves, however. For instance, a single manifold connecting ten source tanks to ten filler machines, would use over a hundred valves to accomplish the control which is necessary and desired.
In the past, it has been conventional to use specially designed valves to control these manifolds, called block-and-bleed valves, sometimes called leak detector valves, with one such valve installed at each manifold intersection. Block-and-bleed valves are particularly applicable to the sanitary industry, because they permit control of flow of different types of fluids through the same valve with double protection against intermixing of those fluids. That is, it may be desirable to have chocolate milk flowing through one part of the valve and white milk through another part, or pasteurized milk through one part and raw milk through another part, or clean-in-place solution through one part and milk or another food fluid through another part. Clearly it is critical that these fluids not be permitted to mix, and regulations require that even failure of a single seat or valve plug not permit that mixing.
The type of valve used in the past functioned generally satisfactorily in most instances. Being a single valve, however, it was required to be extremely complex and expensive, including multiple, coaxial, independently operable actuators and valve plugs. Under certain circumstances these valves were subject to substantial leakage and product waste, and when they did fail in this manner, while preventing mix of different fluids, their maintenance was difficult and expensive.
This invention relates to improvements to the apparatus described above, and to solutions to some of the problems raised or not solved thereby.